Re: [RFC][PATCH 1/10] PM: Add flag for devices capable of generating run-time wake-up events

Alan Stern
2009-11-16T21:00:43Z

On Mon, 16 Nov 2009, Rafael J. Wysocki wrote:

> On Monday 16 November 2009, Alan Stern wrote:
> > On Mon, 16 Nov 2009, Rafael J. Wysocki wrote:
> >
> > > From: Rafael J. Wysocki <rjw@sisk.pl>
> > >
> > > Apparently, there are devices that can wake up the system from sleep
> > > states and yet are incapable of generating wake-up events at run
> > > time. Thus, introduce a flag indicating if given device is capable
> > > of generating run-time wake-up events.
> >
> > This raises the question: Who is responsible for setting the new
> > flag? The code that registers the device?
>
> Yes, in general. The platform.

And for non-platform devices (hot-pluggable, for example)? Presumably
you would want the driver that detects and registers the device to set
this flag.

> Actually, I needed it for PCI, but I thought it would be better to put it at
> the core level.
>
> > What if the kernel can't tell whether or not the device can generate
> > runtime wake-up events?
>
> Do you have any specific examples in mind?

What about Matthew's example of an ACPI GPE which might or might not
cause a runtime wake-up event, depending on the AML code in the BIOS?

> > What if the user wants to override the kernel's setting? Should there
> > be a sysfs attribute controlling the flag?
>
> I have no plans for adding anything like that.

So if the kernel makes a mistake here, the user won't be able to
correct it.

Alan Stern